The invention relates generally to apparatus and methods for promoting chemical processes, and more specifically to an apparatus and method for generating singlet delta oxygen.
Singlet delta oxygen, or O.sub.2 (.sup.1 .DELTA.), is a highly reactive form of oxygen comprising singlet molecular oxygen having an excited energy state, a function of the particular arrangement of electrons around its nucleus, higher than the normal ground state of the more common oxygen molecule O.sub.2 (.sup.3 .SIGMA.). Singlet delta oxygen is particularly useful as a necessary part of a chemical oxygen-iodine laser. It may also be used in waste treatment, purification of potable water, polymerization and chemical synthesis of oxygenated compounds.
Singlet delta oxygen is generally made by contacting chlorine gas (Cl.sub.2) with an aqueous solution of basic hydrogen peroxide (basic H.sub.2 O.sub.2 or BHP, a potassium or sodium hydroxide/hydrogen peroxide solution) in accordance with the equation: EQU CL.sub.2 +H.sub.2 O.sub.2 +2KOH.fwdarw.O.sub.2 (.sup.1 .DELTA.)+2KCl+2H.sub.2 O
Unfortunately, the excited oxygen molecules are unstable and are reduced to their unusable ground state, O.sub.2 (.sup.3 .SIGMA.), by either metal contact quenching, wall quenching, gas phase quenching or liquid phase quenching. Therefore, to generate O.sub.2 (.sup.1 .DELTA.) both efficiently and with high yields, the contacting device, or reactor, for the gaseous and liquid reactants must provide a large interfacial area in a small volume for a short time, followed by rapid separation of the gaseous and liquid phases.
For further efficiency, a large scale singlet delta oxygen generator must provide for good thermal control of the reactor elements, reactants and reaction products/byproducts to prevent efficiency losses from heating due to the exothermic nature of the reactions.
Prior art singlet delta oxygen generators include spargers, which bubble gaseous reactants, such as chlorine gas, through liquid reactants such as basic hydrogen peroxide; sprays, which spray atomized liquid reactants into a cloud of gaseous reactants; and, wetted wall tube systems. U.S. Pat. No. 4,310,502 to Wagner is an example of an improved wetted wall tube system using a static wetted wall mixer comprising intersecting left and right-handed helical mixing elements, an attached liquid/gas separator and a low volume trap for cooling the gas stream to remove H.sub.2 O.sub.2 and water vapor.
The prior art reactors suffer from various deficiencies, especially where large amounts of singlet delta oxygen need to be produced, for example, to satisfy the requirements of field-based oxygen-iodine lasers. Spargers are difficult to control. The bubble sizes cannot be varied and high gas flow rates lead to foaming. Sprays have no thermal control. The droplets heat up and more water vapor is produced than oxygen. Wetted wall tube systems require elaborate liquid distribution systems and extremely large numbers of tubes.
It is thus seen that there is a need for a singlet delta oxygen generator that is simple, efficient, easily controlled and that can be scaled to produce large amounts of singlet delta oxygen.
It is, therefore, a principal object of the present invention to provide a reactor for generating singlet delta oxygen that provides a large interfacial reaction surface in a small volume for a short time, followed by rapid separation of the gaseous and liquid phases.
It is a another object of the present invention to provide a singlet delta oxygen reactor that is easily scaled up to produce large amounts of singlet delta oxygen.
It is a further object of the present invention to provide a singlet delta oxygen reactor that has very good thermal control of the reactor elements, reactants and reaction products/byproducts.
It is a feature of the present invention that it may be modified to perform other processes for generating singlet delta oxygen, such as are described, for example, in U.S. Pat. No. 4,318,895 to Richardson et al.
It is another feature of the present invention that it may be modified to work as a reactor for producing a large variety of other gases that can be produced by the chemical reaction of a gas with a liquid.
It is an advantage of the present invention that its very good thermal control maintains a nearly uniform low liquid BHP temperature that reduces the level of water vapor impurity in the singlet delta oxygen flow and thereby increases overall system efficiency.
It is also an advantage that the straight gas flow passages result in only a small pressure drop.
It is another advantage of the present invention that it is simple to understand, operate and build.